Traditionally, lawn movers are used to cut the grass of lawns in gardens. On lawn movers which are operated by motors, a rotating knife is commonly arranged under a motor of the lawn mover. Such a rotating knife has two cutting edges which sweep over the lawn to cut the grass.
Contemporary robotic lawn movers have been popular in modern gardening. They are constructed to operate on a lawn more or less constantly, and are often energized by solar panels. To enable robotic lawn movers to drive automatically and constantly, they are to be design with low weight and with small rotating mass. For instance, one single large rotating knife would consume too large amounts of energy. Typically instead, a plurality of knife blades are mounted on a rotating disc, e.g. tree blades each 120 degree along a circumference of the disc, and the disc is made of plastic or any other light-weight material. The knife blades are rotatable fixated to the disc by a fixating element, such as a screw. The knife blades are provided with a hole. By mounting a screw through each of the holes, the knife blades will be rotatably fixed to the disc, i.e. the knife blades will be mounted to the disc, but are free to rotate around the holes. In situations where knife blades hit objects, the knife blades will turn around the screw, such that the cutting edges will be turned away from the object. Thereby, the cutting edges will be protected from damages which may cause decreased sharpness. In addition, unintentionally hit objects may be protected from being cut. The screws will be adjusted such that hits with grass straws do not give rise to a turning of the knife blades. Normally, because of the constant operation of the lawn mover, the grass will not be allowed to grow too long and the resistance of the grass will be small.
The knife blades are losing their sharpness after a time period and may be removed to be exchanged, e.g. due to the cutting movement or upon occasional hits of stones and sand. Used blades are then removed after removal of the fixating screws.
However, removal of knife blades, and mounting of new knife blades require tools, e.g. a screw driver, an allen key, or a wrench, and an operator needs access to specific tools during operation. The knife blades need also to be appropriately adjusted, i.e. the screws will be tightened such that the knife blades will be turned by accidental contact with objects but not by contact with grass straws. In addition, robotic lawn movers may be equipped with a considerable amount of knife blades, and performing exchange of knife blades may therefore be time consuming.
Thus, there is a need of a simplified and efficient process for exchange of knife blades on robotic lawn movers.